Language at home and academic performance
The case of Spain
The present study analyses the influence of taking the PISA test in a language different from the one spoken at home on 15-year-old Spanish students' academic performance. In particular, this could be the case of immigrant students and of students living in regions where a co-official language exists alongside the Spanish language. In the analysis of the influence of this divergence between test and home languages on students' academic performance we go beyond correlation by using an instrumental variable methodology. Our results show that students who did not take the test in their home language perform worse in both reading (0.24 standard deviations) and mathematics (0.06 standard deviations). This may suggest the need to adapt the test language so that students have a sufficient level of understanding, to ensure that the measurement of their competences is not biased by their skill in the test language.